1. Field of the Invention
The present disclosure relates to systems and methods for detecting alignment errors, such as, registration and/or stitching errors, of one or more imaging units and/or printheads.
2. Background of the Invention
High-speed printing systems typically include one or more imaging units. Each imaging unit has one or more printheads and a controller controls each printhead to eject ink onto a substrate, e.g., a paper web, to produce an image. In one example, the printing system includes one or more printhead arrays or assemblies, which can be stationary during the production of a print job while the substrate moves at high speed past the arrays. Each printhead of the array(s) generally prints a specific portion or printing swath of an image along a width of the substrate. The printing swaths of the printheads are stitched together so that adjacent printing swaths are properly aligned with each other. Further, many high-speed printing systems include multiple imaging units, each with one or more printhead arrays that are controlled to overprint images onto the substrate in different colors. The overprinted images are overlapped or registered with each other to produce the desired image. Errors in the stitching and/or registration occasionally arise, wherein such errors first have to be detected before they can be corrected, such as, by moving the printheads relative to each other and/or controlling the ejection of ink from the printheads.